1. Field of the Invention
The present invention relates to a variable pressure valve apparatus structured separately with a control probe and a variable pressure valve to feed electric power from the control probe to the variable pressure valve in an electromagnetic way so that the valve is varied in opening and closing by an actuator operated on the fed power.
2. Background Information
The conventional variable pressure valve apparatus uses a magnetic actuator magnetically driven to vary the pressure of valve opening and closing. The magnetic actuator has a multi-pole rotor having at least one magnet fixed integrally on the rotation shaft, and arranged in a main body of the variable pressure valve. Meanwhile, the rotation shaft of the multi-pole rotor has an integral cam engaging a leaf spring. The leaf spring has the other end engaging an opening and closing valve in a ball form. When the rotor rotates, the leaf spring deflects following the cam to have a varied amount of deflection. This varies the application pressure onto the ball valve engaging the other end. The multi-pole rotor is usually submerged in a liquid flowing through the valve. Also, the multi-pole rotor is rotated due to a magnetic force generated from a probe separated from the variable pressure valve. The probe has at least two or more electromagnets. These electromagnets are equidistant from and positioned nearby the rotation shaft of the variable pressure valve. Rotation is given on a same principle as that of the usual step motor. If a pulse current different in phase is given to the electromagnets to sequentially energize them, the multi-pole rotor is given a rotation force due to a magnetic force from the electromagnets. Thus, the multi-pole rotor is rotated stepwise. (See, e.g. Japanese Patent Laid-open No. 40063/1985).
The conventional variable pressure valve apparatus however uses a magnetic actuator to be driven due to a magnetic force. When conducting photographic diagnosis with an MRI (magnetic resonance imager apparatus), the variable pressure valve apparatus is affected by a magnetic force generated by the apparatus and is therefore, subjected to the occurrence of malfunction. Furthermore, the multi-pole rotor of the magnetic actuator is held by a weak force of the leaf spring engaging the multi-pole rotor. Accordingly, if the variable pressure valve suffers an impact, the leaf spring goes out of contact or is weakened resulting in a problem of causing rotation of the rotor. Additionally, because the magnetic actuator is entirely exposed to a liquid passing the valve, there are cases of deposition of ingredients of the fluid in a long term. In particular, where the actuator at its bearing part is in a fluid, there is a problem that rotor rotation is badly affected. Furthermore, because of an absence of a mechanism for stopping the valve from opening, the valve cannot be stopped from actuating even if its operation is unnecessary. In order to prevent the valve from actuating, the valve must be urged by such a force that the valve cannot be moved by fluid pressure. However, there has been a problem that the variable pressure valve apparatus has increased in size with increased power consumption. Because of the absence of a positioning mechanism for efficiently providing a magnetic force of the probe to the rotor, a magnetic force if given to the rotor will not supply sufficient electric power to the rotor, resulting in a problem that the rotor might not rotate normally.
The present invention is provided with position detecting means to efficiently supply electric power without contact, a non-magnetic actuator free from malfunction due to a magnetic force, impact disturbance or deposition of ingredients of a flowing fluid, and a means to disable as required an opening and closing function of a valve and operable with fidelity under an external probe.
In order to avoid an affection of an external magnetic force, an actuator is utilized which has as a drive source a shape memory alloy or piezoelectric element to non-magnetically drive pressure varying means. It was taken in and supply a non-contact power feed system due to an electromagnetic coil utilizing electromagnetic coupling power as required power to operate the non-magnetic actuator. In order to avoid poor operation due to deposition of fluid ingredients on the non-magnetic actuator and short circuit during power feed, an isolation structure is adopted that isolates between a fluid flowing through the variable pressure valve and the actuator and electromagnetic coil. Furthermore, provided are a rectifying lever to forcibly stop valve opening and closing, and a mechanism for enhancing a stationary force by engaging a cam varying spring deflection with a positioning spring so as not to vary the deflection of the spring urging the valve due to impact. An electric power feed system is provided with a primary coil to maximize efficiency on a probe side and a position detecting function to detect a position of a secondary coil on a pressure varying valve side.
In the case that a shape memory alloy is used for the actuator, the shape memory alloy is reduced in size as small as possible for immediate heat conduction, in order to improve the lower in operation speed upon discharge. It is also possible to forcibly accelerate heat exchange due to heating and cooling by contacting the thermoelectric element with the shape memory alloy. This can increase the speed of operation of the shape memory alloy. In order to avoid malfunction of the shape memory alloy due to affection of environmental temperature, the deformation temperature of the shape memory alloy is set higher than an environmental temperature to be assumably exposed routinely. Where heating and cooling by a thermoelectric element, the shape memory alloy can be set to cool and actuate. Thus, the set range of operation temperature broadens, providing a merit of increasing the width of selection.